The present invention relates to a so-called shunt valve, which is applied in a known manner after a laryngectomy performed on a patient, in a surgically produced connection channel between the trachea and esophagus, which is the so-called shunt. This makes it possible for the patient to carry out, along with the air conductance that is necessary for life, also an air conductance for generating sound, i.e. for speech, through a surgically created tracheostomy. If the patient closes the tracheostomy by hand while exhaling, or if the tracheostomy is closed by a tracheostomy valve when a predetermined pressure is exceeded, air can pass out of the trachea into the esophagus, through an artificially produced connection channel, and can be used for the formation of sounds.
Shunt valves function primarily for the purpose of keeping open the artificial connection channel. In addition to that, however, they have an another important function of not allowing secretions and food particles to pass from the esophagus into the trachea, which would otherwise cause severe complications. For this purpose, valves operating on one side have been proposed on the esophagus end of the shunt valve, for example in German published patent application DD-A-275 183 in the form of a flap valve or according to DE-A-32 11 126 in the formation of a tube that is itself closed on the esophagus end, which only provides a valve slit through which air can be conducted from the trachea into the esophagus as desired.
The solutions proposed thus far have, however, only a sub-optimal sealing effect and are hardly convincing in practice. Thus, it is constantly recurring in the known shunt valves that food particles or secretions pass into the trachea, which can cause severe difficulties for the patient.
A voice prosthesis of the generic type according to the construction of French published patent application according to FR 2494581. A also does not create a remedy to improve this situation. This publication shows a voice prosthesis to be applied in a surgically produced connection channel between the trachea and esophagus, which has a tube-shaped part having an open lumen to be turned toward the trachea and a closable lumen to be turned toward the esophagus, which can be closed through a flap valve acting on one end, the flap of which stays in its closed position when there are no opposing forces, and which upon inhalation, in opening the flap, allows an air flow from the trachea into the esophagus. On the esophagus end, the possibility is not to be ruled out that food particles can enter into the tube-shaped part and thus stop up the lumen of the shunt valve or even pass into the trachea, where they can cause severe coughing fits or cases of suffocation.
From U.S. Pat. No. 4,820,304, another voice prosthesis is known in which it is proposed to form on the shunt valve on the esophagus end, a roof-like cover, and which acts against an entry of food particles into the inside of the valve.
In view of this background, an object of the invention presented here is to create a remedy for this situation, i.e. to provide a shunt-valve that shows a decisive improvement compared to the known solutions in regard to sealing function of the trachea from the esophagus. This purpose is achieved through a shunt valve according to the present invention, for which advantageous embodiments are described below.
Accordingly, as an improvement of the shunt valve according to the generic concept described above, it is proposed that (1) the tube-shaped part is provided with a plastic sheath that is physiologically compatible, (2) the pivot area of the flap of the flap valve is substantially completely covered by a roof-like protuberance of the plastic sheath, and (3) an elastic force acting on the flap is produced by a restoring spring that contacts the flap directly at one end, the restoring spring being formed on the roof-like protuberance of the plastic sheath, and urges the flap into the closed position.
The realization of the first feature above in regards to the tube-shaped part leads to the actual core piece of the shunt valve, namely the tube-shaped part, forming more or less a reinforcement for the plastic sheath, which can be made of silicone, for example. The physiological compatibility is thus clearly improved by this. In addition, the inner tube piece can be pulled out of the plastic sheath for cleaning purposes, while the plastic sheath can remain in place.
The second and third features above lead to a clear increase of the safety of the shunt valve according to the invention. The solution of the formed (molded-on) restoring spring is, moreover, especially cost-effective to manufacture, since the restoring spring can form a single-piece component of the remaining plastic sheath.
The active closing of the flap valve through the restoring forces of the restoring spring acting on the flap of the valve offers a considerably higher safety than the passively acting valve members of the known shunt valves, so that the traditional complications do not have to be reckoned with in wearing the shunt valve according to the invention.
The installation position of the shunt valve should be such that the flap opens in the caudal direction, whereas the roof-like protuberance forms a quasi-shield in the cranial direction.
Preferably, the inner tube-shaped part is made of a physiologically compatible metal. This offers the possibility of a sufficient mechanical stability, where the flap of the flap valve on the esophagus end can also be made of metal and have a truncated cone shape, in order to obtain an optimal sealing.
The stability of the position of the shunt valve in the connection channel between the trachea and esophagus can be advantageously increased by forming on the plastic sheath two surrounding flanges, between which the esophagus wall and the trachea wall come to rest. These walls are surgically connected together in the area of the connection channel, for example sewn together, so that both walls lie together between the flanges.